Tuning the C-X...π interaction of benzene-chloroacetylene complexes by aromatic substitutions

The interaction between chloroacetylene (C2HCl) and substituted benzenes has been investigated using density functional theory (DFT), MP2, and CCSD(T)/CBS methods. The results derived from these calculations revealed predominant non-covalent pi...ClC2H interactions in all cases. The predicted interaction energies for substituted benzene/ClC2H complexes span a narrow range from -1.61 to -3.96 kcal/mol, indicating that the pi...ClC2H interaction is comparable in strength to well-documented C-H...pi interactions. The trend for interaction energies was found to be hexafluorobenzene-ClC2H < sym-tetrafluorobenzene-ClC2H < sym-trifluorobenzene-ClC2H < sym-difluorobenzene-ClC2H < benzene-ClC2H < sym-dimethylbenzene-ClC2H < sym-trimethylbenzene- ClC2H < sym-tetramethylbenzene-ClC2H < hexamethylbenzene-ClC2H. We have shown that electron-withdrawing groups weaken the complex, whereas electron-donating groups strengthen the interaction energy of the complex. (C) 2014 Elsevier B. V. All rights reserved.